Under-bath tuyere



Aug. 20, 1968 R. L w, HOLMES ET AL 3,397,873

UNDER-BATH TUYERE Filed Nov. 19, 1965 United States Patent O 3,397,878 UNDER-BATH TUYERE Ronald' L. W. Holmes, New Providence, and Maurice F. Hoffman, Whippany, NJ., assignors to Union Carbide Corporation, a corporation of New York Filed Nov. 19, 1965, Ser. No. 508,709 3 Claims. (Cl. 266-41) ABSTRACT OF THE DISCLOSURE A tuyere for introducing gas beneath the surface of a molten metal bath contained in a metal processing vessel having a refractory lining provided therein with an opening, which comprises: a metal blowpipe extending through such opening having nozzle means for discharging a reactive gas stream into such bath, and a refractory sealing materi-al surrounding such blowpipe. The blowpipe is also provided with gas passage means for simultaneously discharging an annular protective stream of inert gas, through such nozzle means, into the bath in concentric relation with such reactive gas stream. Also, such nozzle means are tapered at the discharge end so as to expose as small a surface area as possible to such bath.

This invention relates to an under-bath tuyere, and more particularly to an inert gas-reactive gas tuyere for metal processing vessels.

The invention provides yan under-bath tuyere for a metal processing vessel having a refractory lining provided therein with an opening comprising a blowpipe extending through said opening, and sealing means including refractory material supporting the business end of the blowpipe adjacent molten metal contained in the vessel. The blowpipe comprises means for discharging a reactive gas stream into such bath of molten metal, and means for simultaneously discharging an annular protective stream of inert gas into such bath in concentric relation with such reactive gas stream for increasing the life of the tuyere.

Such tuyere is especially suit-able for use in the argonoxygen decarburization processes, is inert gas cooled, and permits the introduction of gas mixtures containing high percentages of oxygen near the bottom of a molten metal bath. The tuyere being gas cooled, avoids the need for water cooling in which failure would be catastrophic if located inside the bottom of a vessel containing molten metal. The inert gas flow maintains the parts of the tuyere below the temperature of ignition with oxygen, thereby avoiding damage to the tuyere. Further, the gas is introduced into the molten metal so as to prevent the molten metal from touching the central area of the tuyere. Any solidifying of metal on the exposed tuyere face would shut off gas flow. As a result, the invention increases the life of the tuyere from a few seconds to at least an hour, i.e., the duration of the process.

In the drawing:

FIGURE 1 is a view in vertical section of the lower portion of a steel processing vessel.

FIGURE 2 is a View in cross-section on line 2-2 of FIGURE l.

As shown in the drawing, vessel wall is steel that is provided with a refractory lining 12. The latter has a rectangular opening 14 in which is mounted -a refractory block 16 having a round hole 18 which is concentric `with an opening 20 in the steel wall 10. A refractory cylinder 22 is telescoped in the hole 18 and opening 20, with its outer face 24 ush with face 26 of the wall. A metal body 28 comprising a heat sink has its inner face 30 mating with such faces 24 and 26.

The body 28 has a horizontal passage 32 in line with ice the axial center of the cylindrical block 22. Such body 28 constitutes the base of a blowpipe 36, the front portion of which extends through the cylinder 22 with its front end 38 flush with the inner face 40 of the cylinder 22. The business end of the blowpipe is tapered at 42, and the entire blowpipe is surrounded by refractory packing 44 which is rammed into the annular space 45.

The blowpipe 36 comprises a steel tube 48, the rear end of which is threaded into an inner socket 50 adjacent passage 32 in lbody 28; and in the front end of which outer nozzle 52 is threaded. A steel pipe 54 extends through the entire assembly, being supported at its front end by an inner nozzle 56, which fits within the outer nozzle 52; and at its rear end by packing 58, gland 68 and nut 62 contained in an outer socket 64 in the body 28.

Means for conducting inert gas to annular passage 62 between the pipe 54 and tube 48, includes a vertical gas passage 66 in the body 28 and a gas inlet connection 68. The front end portion of the inner nozzle 56 is tapered to t the tapered inner surface of outer nozzle 52 at 70, but the inner nozzle is uted, providing ports 72 for the flow of inert gas from the blowpipe laterally into the bath in the vessel.

Means for conducting reactive gas to the interior of pipe 54 includes a gas inlet fitting 74 attached to the outer end of the pipe 54. The reactive gas is preferably a mixture of argon and oxygen, While the protective gas is preferably argon, although any suitable non-reactive gas or vapor, such as nitrogen, helium, etc., may be used provided it is inert in the process.

The tuyere provides for annular or surrounding ow of inert gas to protect the tuyere, and a central orifice for introducing oxygen or inert gas-oxygen mixtures. It is preferred that the tuyere be placed in the bottom or side of a vessel containing molten met-al to be decarburized. The tuyere should be surrounded by refractory with a radial thickness of several inches. Thus, the only metal surfaces of the tuyere exposed to molten metal are the small annular face 76 surrounding the main orifice, and the annular rim 78 surrounding the inert gas annulus. These surface areas are minimized by tapering the nozzle parts tow-ard the end of the tuyere.

The gases introduced through the tuyere must be flowed at a rate to maintain absolute pressures before the tuyere at least twice the ferrostatic head of the molten metal plus atmosphere pressure or, in other words, maintain greater than critical gas flow through the tuyere.

The tuyere provides an annular flow of inert gas to pick up heat conducted through the refractory to the metal tuyere. The annulus gas ow is turbulent to take advantage of the most efficient heat transfer. Su'icient gas is passed through the annulus to maintain the outer tube of the tuyere at less than 1000 F. The inner tuyere tube is maintained at about F.

The inert gas stream provides a protective shield or buffer in front of the tuyere which prevents molten metal from reaching the tuyere face, and also reduces the temperature of the molten metal exposed to the tuyere face below the temperature normally present with only oxygen decarburization.

After processing is completed Vand the gas flows are turned 01T, the cool tuyere parts provide adequate heat sink to solidify any molten metal which ftows into the tuyere nozzles. Then, after the metal is poured from the vessel, a rebuilt tuyere replaces the metal-sealed one from the previous heat.

What is claimed is:

1. An under-bath tuyere for introducing gas beneath the surface of a molten metal bath contained in ya metal processing vessel having a refractory lining provided therein with an opening, which comprises: a metal blowpipe extending through said opening into the vessel and having, at its discharge end, nozzle means for discharging -a reactive g-as stream into a bath of molten metal, and sealing means including refractory material surrounding said blowpipe, said blowpipe also provided with gas passage means for simultaneously discharging an annular protective stream of inert gas, through said nozzle means, into said bath in concentric relation with said reactive gas stream, said nozzle means being tapered at the discharge end so as to expose as small a metal surface area as possible to said bath.

2. A tuyere as defined by claim 1, in which said annular stream is obtained by the merger of a plurality of smaller streams that are discharged by a plurality of ports arranged in a circle in said blowpipe adjacent the business end thereof.

3. A tuyere as dened by claim 1, in which the business end of said blowpipe comprises tapered concentric nozzles of metal for discharging such gas streams, so that the annular surface areas thereof facing the molten metal of the bath are as small as possible.

References Cited UNITED STATES PATENTS 2,480,394 8/ 1949 Cavers et al. 266-41 3,236,629 2/ 1966 Agarwal et al 266-41 X FOREIGN PATENTS 1,031,653 6/ 1966 Great Britain.

884,240 7/ 1953 Germany. 203,777 8/ 1962 Sweden. 469,349 11/ 1950 Canada. 411,703 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner. 

